Composite fiber with reversible crimp



June 12, 1962 TSE CHENG wu 3,038,238 I COMPOSITE FIBER WITH REVERSIBLE CRIMP 2 Sheets-Sheet 1 Filed Nov. 20, 1958 ATTORNEY COMPOSITE FIBER WITH REVERSIBLE CRIMP Filed Nov. 20, 1958 2 Sheets-Sheet 2 h INVENTOR 'ITSE CHENG wu ATTORNEY 3,038,238 Patented June 12, 1962 Free Pont de Nemonrs and Company, Wilmington, Del., a corporation of Delaware Filed Nov. 20, 195$, Ser. No. 775,193 8 Claims. (Cl. 2882) This invention relates to synthetic textile fibers and particularly to improved crimped composite filaments.

Most of the synthetic textile fibers are relatively straight and are thus not adapted to being spun into yarn on either the cotton or woolen system or to be used in bulky continuous filament yarns. Various methods have been proposed to produce crimped synthetic filaments. These methods usually comprise mechanical treatment of filaments spun in a normal fashion and/ or the use of specific spinning conditionsor aftertreatments which bring about dilferential physical properties across the cross section of the single filaments.

Newer proposals of producing an improved crimp in synthetic fibers comprises co-spinning of two or more different materials so that they form a unitary filament which contains the components in an eccentric relation over the cross section of the filaments. Thus, when two materials are used which possess substantially different physical properties, such as for example, different residual shrinkage, a crimp is brought about by the application of a suitable aftertreatment to the spun and drawn composite filaments. However, such self-crimped filaments often have the disadvantage that part of the crimp is lost or becomes unavailable in fabrics composed of such filaments, due in large to the fact that the filaments become compacted and lose freedom of movement in the fabric resulting in fabrics of reduced covering power or leanness. Such fabrics do not lend themselves to recovery from distortion and in general cannot be adapted to the normal fulling operations as employed with wool for example.

One object of this invention is to produce a novel crimped composite filament having crimp reversibility such that the crimp intensity is responsive to treatments of varying pH. Other objects will become apparent from the following description.

In accordance with the invention a composite filament is prepared containing at least two synthetic polymer components eccentrically arranged. One of such components contains at least 100 milliequivalents (meq.) of carboxylic groups per kg. of polymer and one other of said components contains at least 100 meq. of basic groups per kg. of polymer. The composite filament is crimpable from the straight state upon shrinking and has crimp reversibility upon treatment with and subsequent removal of water. Preferably there is a difference of at least 50 meq. between the acid and the base levels and more preferably the acid concentration is greater than the base.

By the expression synthetic polymer" is meant a polymer that has been man-made from relatively low molecular weight compounds (monomers) by addition polymerization methods. By the expression carboxylic groups is meant the free acid or their salts with metals, ammonia or amines.

The new improved filaments of this invention may be obtained by spinning together two or more critically selected synthetic polymeric materials, at least one of which is fiber-forming. The materials are co-spun to form a single composite filament having two or more distinct zones over its cross section, said zones extending through the entire length of the filament in eccentric fashion. One, or alternatively, part of or all the components form the surface of the single composite filament.

(For convenience, the following discussion will refer to two-component filaments although the filaments may, if desired,

have more than two components.)

Composite side by side filaments may be extruded through a spinneret more particularly described below.

Referring to the drawings:

FIGURE 1 is a central cross-sectional elevation of a spinneret assembly which can be used to make the composite filaments of this invention;

FIGURE 2 is a transverse cross-sectional plan view of the apparatus of FIGURE 1 taken at 22 thereof and showing details of the top of the back plate;

FIGURE 3 is a transverse cross-sectional plan view taken at 3-3 of FIGURE 1 showing details of the bottom of the back plate;

FIGURE 1A is an enlarged portion taken from FIG- URE l to show details of the spinneret at the spinning orifice; and

FIGURES 4, 5, 6, and 7 show greatly magnified crosssections, i.e., sections perpendicular to the filament axis of typical filaments of this invention produced by dry spinning. In these drawings One component is shaded to show the separation between components.

With reference to FIGURE 1, the bottom spinneret plate 2 which contains a circle of orifices 3 is held in place against back plate 1 by retaining rings 12 and 14 and by bolt 13. A fine-mesh screen 4 e.g., 200 mesh per inch, is pressed into position between, and serves .as a spacer between, spinneret plate 2 and back plate 1. Back plate 1 contains two annular chambers 8 and 9 which are connected to suitable piping and filtration apparatus (not shown) to receive different spinning compositions. Lead holes 11 go from annular chamber 9 to annular space 7. lead holes 10 lead from annular chamber 8 to annular space 6. Annular spaces 6 and 7 are separated by wall 5 which is disposed above orifices 3 and spaced from spinneret plate 2 by screen 4 to permit free and contiguous passage of the spinning fluids from annular spaces 6 and 7 through orifices 3, the mesh of screen 4 being fine enough to permit spinning fluid passage through orifices 3, as shown in detail in FIGURE 1A.

In FIGURE 2 are shown four lead holes 10 and four lead holes 11 equally spaced within the concentric chambers 8 and 9, respectively.

In FIGURE 3 are shown the concentric inner and outer annular spaces 6 and 7 and the fine-mesh screen 4 partially in section.

Operation of the described apparatus in the practice of this invention is readily understood. Separate spininng materials are supplied to the inner annular chamber 9 and outer annular chamber 8, respectively, of the back plate; the former flows from chamber 9 through the lead holes 11 into the inner annular space 7 and thence through screen 4 and orifice 3 to form. a part of a composite filament, while the latter passes through the lead hole 10' to the outer annular space 6 and then through screen 4 and the outer side of the orifice 3 to form the other part of the composite filament.

The crimp reversibility of the filaments of this invention are determined by the following test.

A single filament is separated from a single end or a tow of drawn, unrelaxed fibers. A three-inch length of the filament is attached to opposite sides of a rectangular copper wire frame with 30% slack between the ends. The rack and filament is then boiled oif for 15 minutes to develop the crimp. The crimped filament is then transferred to a special viewing holder by taping or gluing the ends so that about 10% slack is present and the filament length between the clamped ends is approximately 2.5

r, inches. The filament and viewing holder is then mounted vertically in a stoppered test tube containing desiccant. The tube is stored vertically overnight (1824 hours) at 70 C. Following this conditioning period to dry the filament the tube is then brought to room temperature (approximately 25 C.). After allowing 30 minutes for cooling, the total number of crimps in the filament between the fixed ends are counted. In counting, any crimp reversal points present are ignored. The desiccant is then removed from the glass tube, the tube filled with water and stored vertically at 70 C. for 6 hours. The number of crimps in the wet fiber are counted as above. The cycles are repeated as required to obtain reproducible results. The change in crimps/inch of crimped length from 25 C. dry to 70 C. wet expressed as A c.p.i. is obtained by the following equation where the signal of A c.p.i. is ignored.

number of crimps (25 C. dry) A number of crimps (70 C. wet) total filament length (crimped) at 25 C. dry

The equilibrium crimp reversibility (ECR) is expressed as the relative change in crimps from dry to wet as calculated by:

No. of crimps (25 dry) No. of crimps (70 Wet) X 100 No. of crimps (25 dry) Another means of testing for crimp reversibility utilizes the actual turning of a crimped filament. The crimped fibers of this invention may contain helices which reverse direction at irregular intervals. Accurate measurements of crimp reversibility by this method require samples without these reversals. Preparation of such filament samples was accomplished by a pretwisting of the filament (prior to exposure to the crimping medium) to the same degree as the crimp frequency found by examination of similar filaments crimped without pretwisting. For crimp reversal measurements, the pretwisted filament was crimped free of tension by immersion in boiling water or other suitable shrinking media. The crimped filament was then suspended in a tube and kept from floating or bending by a small weight (1 milligram) attached to the lower (free) end and insuflicient to remove crimp, the weight being pointer-shaped to permit measuring and counting rotations of the pointer during crimping and uncrimping. The filament was treated successively to 5 cycles each consisting of a 5-minute exposure to 90 C. water followed by -a -minute drying period in 90 C. moving air. The revolutions of the pointer (which are equivalent to the crimp changes) for the drying and Wetting portion of each cycle, were averaged for the 5 cycles and expressed as turns per inch (t.p.i.) of crimped dry filament and are referred to hereinafter as crimp reversibility. Values from at least three filaments tested as above were averaged to obtain the crimp reversibility of a fiber.

Crimp reversibility which is a characteristic of the filaments of this invention is observed by the squirming of the filaments upon both application and removing of the swelling agent. The value of this crimp reversibility is evidenced by the ability of the filaments in yarns, when embodied in a fabric, to squirm or twist around in the fabric under the influence of a swelling agent such as water (and also on removal of the swelling agent), but, nevertheless, to regain the original crimp in the fabric with removal of the swelling agent, as by drying. Fabrics containing these filaments acquire a high degree of fullness or covering power as a result of the swelling treatment and retain or even increase this fullness after being subjected to such treatments repeatedly. The change in crimp, with change in pH, olfers additional degrees of freedom in finishing fabrics made of the filaments of this invention.

Another property of the filaments of this invention that AECR- is of great importance is their ability to recover from compaction. The following test is used to measure this P p y,

Crimped fibers were cut in 2-inch lengths, hand carded and made into pellets weighing 0.20 gram. The pellets were placed into a cylinder (0.5 inch diameter hole), heated to C., Wet with 1 ml. of water and compressed under a freely sliding piston that exerted 1 p.s.i. for two minutes. The height of the pellet under compression was measured. The compressed pellets were removed from the cylinder and: (1) allowed to recover in dry air for 24 hours and then (2) exposed to steam at atmospheric pressure for 1 minute. The heights of the recovered pellets were measured after treatment (2) and the recovery from compaction calculated:

(height of recovered pellet compressed height of pellet) X Compressed height of pellet Recovery:

The expression intrinsic viscosity with the symbol n as used herein signifies the value of ln(n) at the ordinate axis intercept (i.e., when c equals 0) in a graph of EXAMPLE I Acrylonitrile and acrylic acid were fed to a conventional continuous polymerization system (i.e., constant environment) at a ratio of 9/ 1 and copolymer with an n of 1.4 obtained. The polymerization conditions and recovery procedure were such that the acrylic acid units were in the copolymer in the free acid form. The copolymer contained 9% acrylic acid by analysis (1230 meq. of acid per kg. of polymer).

A mixture of acrylonitrile and N,N-diethylaminoethyl methacrylate in the ratio of 9/1 (540 meq. of base per kg. of monomer mix) was similarly fed to a polymerization system under an acid pH so that the resulting copolymer with an n of 1.6 had the methacrylate units present as the sulfate salt. The copolymer contained 6% N,N-diethylaminoethyl methacrylate (325 meq. of base per kg. of polymer) by analysis.

29 and 27% solutions in dimethylformamide (DMF) of the above two polymers respectively were simultaneously extruded at C. through a spinneret similar to that described in the accompanying drawings having 60 orifices of 0.007 inch in diameter. The solutions were fed to the spinneret so that the copolymer of acrylonitrile and acrylic acid component in each filament faced the cell wall. The composite (side-by-side) filaments were extruded down into a spinning cell 9 inches in diameter by 19 feet long with a concurrent fiow of a mixture of carbon dioxide and nitrogen that was at a temperature of 320 C. as it entered the cell around the spinneret, the walls of the spinning cell being maintained at C. and the yarn was Wound up at 200 y.p.m.

The 600 denier as-spun yarn was drawn to 4.5 times its original length (i.e., 4.5x) in water at 9598 C. Which simultaneously extracted the residual DMF in the yarn. Upon boiling in water the yarn developed 19.2 (helical) crimps per inch of extended length and had a denier per filament of 3.7. The crimped fiber displayed 258% recovery from compression upon steaming.

Crimped lengths of yarn without reversal points prepared for evaluating the crimp reversibility of the yarns gave very unusual results. A crimped length of the filament was placed in a bath at pH 1 which caused it to turn /z turn in a clockwise direction. Upon placing the sample in water, it turned an additional 3% turns clockwise, upon transferring to a sodium hydroxide solution (pH 11) the fiber turned 39 turns in a counter-clockwise direction.

A second sample of crimped filament was placed in a bath of Na CO and NaHCO at pH of which caused the filament to describe 78 counter-clockwise turns; upon transfer to a buttered bath at pH 7, the filament then turned 23 turns clockwise and on changing the bath to a pH of 4, the yarn turned an additional 34 turns in a clockwise direction.

Another filament was placed in a bath at pH 7 which caused it to turn 5 turns in a clockwise direction; transferrance to a bath at pH 1 resulted in 1% additional clockwise turns and the replacement of this bath with a solution of sodium hydroxide (pH 10) caused the filament to describe 30 counter-clockwise turns.

The above data-which is not directly comparable due to ditIerences in technique and time of treatment'does indicate qualitatively that the filaments of this invention display a novel change in crimp intensity with changes in pH.

EXAMPLE II This example demonstrates the superiority of the filaments of this invention over other composite filaments.

The crimp properties of various self-crimped composite filaments were determined after a one hour treatment in a hydrochloric acid solution at pH 1%, a 1% sodium carbonate (Na CO solution (pH 11) and in water all at 90 C.

Item A is the filament of Example I.

Item B was made in a manner similar to Example I except that the acrylonitrile/diethylaminoethyl methacry late copolymers was replaced with a homopolyrner of acrylonitrile of n 1.5.

Item C was prepared similar to Example I except that the acrylic acid copolymer was replaced with the homopolymer of acrylonitrile of n 1.5. The crimp and crimp reversibility were so low as compared with item A under optimum conditions that the other conditions were not tried.

Item D is a two-component fiber prepared in a manner similar to Example I consisting of the homopolymer of acrylonitrile of n 2.0 as one component and a copolymer of acrylonitrile and styrene sulfonic acid 96/ 4% by weight composition (286 meq. of acid groups per kg. of copolymer) as the other component. The items B, C, and D are used for comparative purposes only and are not examples of this invention. The results of the tests are shown in Table I.

Table l CRIMP PROPERTIES AFTER INDICATED TREATMENT EXAMPLE III A copolymer was made by continuously polymerizing a 95/5 mixture of acrylonitrile and acrylic acid (685 meq. of acrylic acid per kg. of monomer mixture) to obtain a polymer with an n of 1.8.

A second copolymer was made by continuously polymerizing an 80/20 mixture of acrylonitrile and N,N-diethylaminoethyl methacrylate to obtain a polymer of n 6 1.6. The monomer mixture contained 1080 meq. of base per kg.

25 and 27% solutions in DMF of the above two polymers respectively were simultaneously extruded, drawn, and relaxed as in Example I to produce composite (side by-side) filaments that had 17.9 crimps per inch of extended length and a denier per filament of 2.9. The yarn had a crimp reversibility at C. of 0.8 t.p.i.

A typical filament from this yarn had 12 crimps per inch of crimped length dry after boiling oif. A onehour treatment at 90 C. in an HCl solution at pH 1.5 followed by drying afforded 13 crimps per inch of crimped length. The filament was then treated for one hour in a 1% solution of Na CO at a pH of 11.5 at 90 C., the filament washed and dried to produce 38 crimps per inch of crimped length in the dried filament.

EXAMPLE IV This example illustrates new and novel products made from the filaments of this invention.

A 90/ 10 mixture of acrylonitrile and diethylaminoethyl methacrylate was continuously polymerized to make a copolymer of n 1.55 and a 26% solution in DMF prepared for spinning.

An 87/ 13 mixture of acrylonitrile and acrylic acid (1750 meq. of acid per kg. of monomer) was continuously polymerized to produce a copolymer of n 1.36 in which the acrylic acid was in the acid form (i.e., no basic short stop or aftertreatment used) and a 26% solution in DMF prepared for spinning.

The two solutions prepared above were simultaneously extruded as in Example I, and the yarn drawn. A sample 'of the yarn relaxed by boiling in water had a tenacity 1.8 g.p.d., an initial modulus of 19.5 g.p.d., an elongation at the break of 37%, a crimp index of 11.6%, a crimp intensity of 24.4 crimps per inch of extended length, a A c.p.i. of 8.7, and an ECR of 36.4%.

Some of the unrelaxed yarn was cut to 3" staple. The unrelaxed staple was carded to form a batt of about 5 to 10 inches having a thickness of 0.3 inch. When this batt was relaxed in steam or by boiling in water, it shrank down to a dense, felt-like structure (2.2 x 5 x 0.25 thick) in which the fibers were so tightly bound that they could not be removed except by breaking.

Two of the polymeric components of the composite filaments of the present invention should be selected so that they have a difference in shrinkage of at least 1% and a difference in reversible length change of more than 0.4% (as determined on single component filaments measured at equilibrium at 25 C. dry and 70 C. wet). Such a critical selection of components yields a composite filament that will develop at least 5 crimps per inch of extended length and has an equilibrium crimp reversibility (25 C. dry to 70 C. wet) of at least 1% and preferably at least 5% Polymers suitable for use as a component of the yarns in this invention may be found among all types of addition type polymers such as polyhydrocarbons, polyethers and those made from ethylenically unsaturated monomers such as acrylonitrile, styrene, vinyl chloride, vinylidene chloride, vinyl acetate and their copolymers with each other and other copolymerizable monomers.

Polymers containing 80% or more combined acrylonitrile are especially preferred due to their resistance to chemical reagents, ultra-violet light degradation and outstanding physical properties. Numerous monomers can be copolymerized with acrylonitrile as disclosed in Jacobson US. 2,436,926 and in Arnold US. 2,456,360 to produce copolymers useful herein.

Such polymers can contain minor amounts of a sulfonic acid obtained from ethylenically unsaturated sulfonic acids as the methallyl sulfonic acids and others as disclosed in US. Patents 2,527,300 and 2,601,256 for purposes of dyeability, etc.

The polymeric component containing at least meq. of carboxylic groups per kilogram of polymer for use in this invention may be formed by the polymerization of a monomer containing carboxylic groups, by the copolymerization of a neutral monomer and an acidic monomer, by the blending of an essentially neutral and an acidic polymer or by chemical treatment of an essentially neutral polymer as for example oxidation or hydrolysis to produce carboxylic groups along its chain. A copolymer containing carboxylic groups is preferred for use in this invention.

In addition to acrylic and methacrylic acids, suitable addition type monomers may be found among the followot-Chloracrylic acid Itaconic acid Fumaric acid Maleic acid Citraconic acid Crotonic acid Vinyl benzoic acid Allyl acetic acid Cinnamic acid Dihydroxy fumaric acid Carboxylic groups can also be obtained in the polymer by degrading a polymer or chemically altering it by various means, e.g., partial acid hydrolysis of polyacrylonitrile, and the basic hydrolysis of ester groups on the side chain of a polymer.

The polymeric component containing at least 100 meq.

of basic groups per kilogram of polymer can be obtained by polymerizing a basic monomer, by copolymerizing an essentially neutral monomer with a basic monomer, by blending a polymer containing basic groups with an essentially neutral polymer or by chemical modification of a polymer to introduce basic groups thereon.

The use of copolymers containing basic groups is preferred for use in this invention. Monomers such as 2-vinylpyridine, Z-methyl-S-vinylpyridine and others of that type as disclosed in 2,491,471, issued to Arnold, p-dimethylaminomethyl styrene, vinyl ethers of amino alcohols such as betadiethylaminoethyl vinyl ether, esters of acrylic and methacrylic acid with amino alcohols such as N,N-diethylaminoethyl acrylate, and polymerizable quaternary ammonium compounds, such as allyltriethylammonium chloride, vinylpyridinium chloride, allylpyridinium bromide, methallylpyridinium chloride, and others as disclosed in Price U.S. 2,723,238, betavinyloxyethyl dicarbornethoxyethyl methylammonium chloride and others as disclosed in Albisetti and Barney, U.S. 2,729,622. and others.

Although the polymers containing basic groups are preferably made by copolymerization, it will be obvious to those skilled in the art that such basic groups can arise from the after-treatment of the polymer or of the fiber, as for example, the reduction amination of poly mers containing ketone groups made from such monomers as methyl vinyl ketone, isopropenyl methyl ketone and the like as disclosed in Ham U.S. 2,740,763 or by the quaternization of a nitrogen group in a solution of a copolymer, such as a copolymer of acrylonitrile and 2-vinyl pyridine as shown in Ham U.S. 2,676,952 or by exposure of a copolymer containing a methallyl haloacetate to quaternization conditions in a spinning solution as disclosed in Ham U.S. 2,656,326.

Although this invention has been illustrated by the use of side-byside structures, a structure which has a core completely and eccentrically surrounded by a sheath is applicable. Such filaments are conveniently spun using a spinneret similar to that shown in coassigned and copending U.S. application Serial No. 519,031, filed .lune 30, 1955, by J. Kilian, now U.S. Patent No. 2,936,482.

Composite filaments prepared for use in accordance with the present invention may be subjected to a drawing (permanent stretching) operation in order to impart to the filaments the desired physical properties as tenacity, elongation and initial modulus. Although drawing may affect shrinkability and the reversible length change of a filament, crimped filaments with a reversible crimp have been made from dry-spun filaments without a drawing treatment. The conditions applied to drawing the spun multi-component filaments may vary in wide limits. The drawing characteristics of the components can readily be determined from those of monocomponent filaments of each of the component polymers of the composite filaments. The drawing can be accomplished in accordance with known principles applicable to the particular polymers of the composite filaments and, in general, the composite filaments are drawn at least (i.e., to 150% of original undrawn length) and preferably about 2-8 times the original lengths. The extent of drawing will, of course, also depend somewhat upon the nature of the particular polymers used in the composite filaments and upon the type of eccentric relationship between those polymers in the composite filament.

In considering the extent of drawing, one should take into consideration the amount of draw which may be effected during the spinning of the filaments, and, in fact, the desired amount of drawing may be effected during spinning rather than as a separate drawing step following the windnp of the filaments from the spinning operation.

The shrinkage of the composite filaments in order to effect crimping, may be carried out by the use of any suitable known shrinking agent. Shrinking will ordinarily be carried out by the use of hot aqueous media such as hot or boiling water, steam, or hot highly humid atmosphere, or by the use of hot air or other hot gaseous or liquid media chemically inert to the polymers of the composite filaments. The shrinking temperature is generally in the neighborhood of C. but may be higher or lower, e.g., 50 C. up to about C. or even up to a temperature not exceeding the melting point of the lowest melting polymeric component of the fiber.

The invention is particularly directed to filaments and yarns (i.e., bundles of filaments) having deniers of the magnitude used in textiles. It is preferred that the filaments of this invention have a denier of 1 to 10 (inclusive) and that the yarns of this invention have a denier of 30 to 8,000 (inclusive).

Although the process of this invention has been illustrated by dry spinning it will be obvious to one skilled in the art that other means of spinning can be used as melt, plasticized melt and wet spinning.

The unusual crimp levels of the filaments of the invention afford useful products as felts, pile fabrics, and nonwoven fabrics of various types. Fabrics made from yarn containing the filaments of the invention exhibit unusual elastic properties. The shrinkage accompanying the higher crimp levels of these filaments makes them useful as the high-shrinking component in a high-low shrinkage blend of staple fibers, for example, the fibers can be stock dyed, blended with a low shrinking staple and then treated with a base.

I claim:

1. A novel composite filament crimpable from a straight state upon relaxation by shrinking and exhibiting crimp reversibility characterized by squirming of said filament upon treatment with and removal of a swelling agent, said crimp reversibility being such that the crimp intensity of said filament is responsive to treatments of varying pH, said filament being comprised of at least two components of different synthetic addition polymers at least one of which is a fiber-forming polymer, said components being eccentrically disposed towards each other in distinct zones with adjoining surfaces being in intimate adhering contact with each other, each of said components extending throughout the length of said filament, one of said components having at least 100 milliequivalents of carboxylic acid groups per kilogram of polymer chemically bonded to the polymer chain and one of said components having at least 100 milliequivalents of basic groups per kilogram of polymer chemically bonded to the polymer chain, two of said components having a difference in shrinkage of at least 1% and one of said components having a reversible length change after shrinkage greater than 0.4% when treated with a swelling agent with said component substantially returning to its original length upon removal of said swelling agent.

2. The filament of claim 1 wherein there is a difference of at least 50* milliequivalents between the acid and the basic levels of the polymeric components.

3. The filament of claim 1 in which the zones are in a side-by-side relationship.

4. The filament of claim 1 in which the zones are in a sheath-core relationship.

5. The filament of claim 1 having two components, one of said components being a copolymer of acrylonitrile and acrylic acid and the other of said components being a copolymer of acrylonitrile and N,N-diethylaminoethyl methacrylate.

6. The filament of claim 5 wherein there is a difference 10 of at least milliequivalents between the acid and the basic levels of the respective polymeric components.

7. The filament of claim 5 wherein the two distinct zones are in a side-by-side relationship.

8. The filament of claim 5 wherein the two distinct zones are in a sheath-core relationship.

References Cited in the file of this patent UNITED STATES PATENTS OTHER REFERENCES Serial No. 373,140, Graumann et al. (A.P.C.), published April 27, 1943.

Organic Chemistry (Ray Q. Brewster), published by Prentice-Hall, Inc. (New York), copyright 1953, pages 215 and 248 relied on. 

1. A NOVEL COMPOSITE FILAMENT CRIMPABLE FROM A STRAIGHT STATE UPON RELAXATION BY SHRINKING AND EXHIBITING CRIMP REVERSIBILITY CHARACTERIZED BY SQUIRMING OF SAID FILAMENT UPON TREATMENT WITH AND REMOVAL OF A SWELLING AGENT, SAID CRIMP REVERSIBILITY BEING SUCH THAT THE CRIMP INTENSITY OF SAID FILAMENT IS RESPONSIVE TO TREATMENTS OF VARYING PH, SAID FILAMENT BEING COMPRISED OF AT LEAST TWO COMPONENTS OF DIFFERENT SYNTHETIC ADDITION POLYMERS AT LEAST ONE OF WHICH IS A FIBER-FORMING POLYMER, SAID COMPONENTS BEING ECCENTRICALLY DISPOSED TOWARDS EACH 